It is common to make tablets in rotary tablet presses or rotary tabletting machines. Machines of this kind have a rotor with a die-plate which has a series of dies, further comprise upper and lower rams which interact with the dies, and at least one pressure station in which the rams are forced against the material filled into the die. This is done during the rotation of the rotor, which is driven by an appropriate driving mechanism. Prior to the compaction process, the dies require to be filled with the material to be compacted (powder). This is accomplished continuously, with the rotor rotating, in a so-called feed shoe or a filling assembly the arrangement of which is stationary.
It is known that such a tablet press has associated therewith a measuring device which records substantial data during production and processes it in a plant computer. The data includes the number of revolutions of the rotor, the maximum compression forces in the pressure station and possibly the run of compression forces in the pressure station, i.e. as associated with the individual pairs of rams. Subsequent measure checks of the ejected tablets for their weight, thickness, and hardness will determine whether the desired parameters have been achieved. If not, it is necessary to vary the charge, compression force or the like. Devices and methods for the control and adjustment of tablet presses to obtain optimum results are adequately known in the state of the art.
The development of tablets, inter alia, involves determining the compression characteristic of the material requiring compaction. At this stage, the product volumes which initially are available are very small and, in addition, are very expensive in both production and material so that production loses need to be kept low during compression.
It is known to carry out compression tests using specific laboratory-type presses. Those mostly are minor-size eccentric presses which allow to produce one tablet each in each compression process. Here, the drawback is that such laboratory-type presses exhibit a compression behavior different from than that of rotary tablet presses which are employed for production. This is why the results of the compression tests cannot be readily transferred to a producing rotary press.
The benefit inherent to a producing rotary press is that the data determined during the compression tests can be transferred directly to tablet production. Furthermore, all settings of the rotary press from the compression test can be taken over for use in production.
Common rotary presses have a feed shoe or an adequate filling device as was described above. To allow such a filling assembly to fill the dies with material in a constantly regular fashion its volume requires to permanently be filled with a basic charge of material to undergo compression even if only a small number of tablets is to be produced. Thus, rotary presses always need to maintain an amount of compression material requiring compaction which is larger than is necessary for the compression test proper.
It is the object of the invention to specify a method for test pressing tablets which can be implemented under the conditions of production, on one hand, and can make do at a minimum expense of compression material, on the other.